Vinyl alcohol-vinyl acetate copolymers are used in many fields such as fiber processing, paper processing, films, and adhesives, as well as dispersants and binders. Vinyl alcohol-vinyl acetate copolymers are commonly obtained by direct saponification of a polyvinyl ester polymer such as polyvinyl acetate with an alkali or an acid. In saponification using an alkali, the saponification reaction is stopped using an acid. In saponification using an acid, the saponification reaction is stopped using an alkali. Patent Literature 1, for example, discloses a method in which a colloidal solution of silicic anhydride is added after saponification using an alkali or an acid.
However, vinyl alcohol-vinyl acetate copolymers obtained by a conventional method have poor solubility in a solvent, and problematically fail to provide a desired effect, in particular, when used together with an aqueous solvent.